The present invention generally relates to mobile communication networks, including cellular-type wireless networks, and, more particularly to a method and computer program for assigning and managing priority for location services in a mobile communication network.
Mobile Communications Networks
FIG. 1 (Prior Art) illustrates a block diagram of a mobile communications network 10 comprising a terminal device, illustrated as an originating mobile phone 12, coupled by an RF communication link to an originating network 14. The terminal device is preferably a mobile phone 12, but could be any wireless communication device such as a pager, a Personal Digital Assistant (PDA), or a Mobile Computing Device (MCD), for example, but may also be a fixed wireless device. The mobile phone 12 may operate based on any number of communication standards including AMPS, TDMA, D-AMPS, GSM, IS-95, or third generation (3G) protocols, for example.
The originating network 14 is seen to be coupled to a transit network or communication link 16, which may comprise a public switched telephone network (PSTN), but could also comprise of other networks including an Internet Protocol (IP) core network, an Asynchronous Transfer Mode (ATM) core network, or an optical network, for example. The transit network 16 interfaces and communicates electrical signals including digitized voice calls between the originating network 14 and a destination network 18. Destination network 18 may be the same as, or different than, the originating network 14, and thus may comprise AMPS, D-AMPS, TDMA, GSM IS-95, or 3G networks such as UMTS. Terminating network 18 is coupled to and services, via a Radio Frequency (RF) link, a destination terminal device, shown to be a mobile phone 20.
The originating network 14 is seen to include a base transceiver station (BTS) 30 serving via a radio frequency (RF) link the originating mobile phone 12. Each BTS 30 services multiple mobile phones 12, although only one is shown for purposes of illustration and clarity. Each BTS 30 also includes a Location Measurement Unit (LMU) 22 (the LMU 22 may also be physically located outside of the BTS 30).
The LMU 22 measures the distance between the mobile phone 12 and the LMU 22 and reports the distance to a Base Station Controller (BSC) 32. Accordingly, originating network 14 further includes a BSC 32 and a Mobile Switching Center (MSC) 34, which can communicate with each other via Direct Transfer Application Part (DTAP) messaging. The network 14 is connected through the MSC 34 to a Gateway Mobile Location Center (GMLC) 36, and communicates with Mobile Application Part (MAP) messaging protocol. The GMLC 36 provides the hardware connections needed to interface the network 14 with the transfer network 16, and houses selected processing functions as well. In addition, the GMLC 36 interfaces to users of a location service that is seeking the location of a mobile phone or other terminal device, performs user authorization tasks, and also forwards positioning requests to the mobile phone""s current mobile network.
Likewise, the GMLC 36 communicates with a Serving Mobile Location Center (SMLC) 38 via Mobile Application Part (MAP) messaging. The SMLC 38 provides the network resources needed to process calls in the network, and particularly to locate a mobile phone, and is directly associated with the MSC communicating with a mobile station that is being located. More particularly, the primary task of the SMLC 38 is to decide upon a positioning method to use to estimate the location of a mobile phone (various methods are discussed below). Note that the BTS 30 and BSC 32 are sometimes collectively referred to as a Base Station Subsystem (BSS).
The BSC 32 interfaces voice calls between multiple BTSs 30 and MSC 34, wherein BSC 32 typically serves multiple BTSs 30, and, similarly, MSC 34 services multiple BSCs 32. MSC 34 includes a visitor location register (VLR) which includes and stores various information regarding the mobile phones 12 currently being served by the originating network 14.
The destination network 18 includes a BTS 40 serving the destination mobile phone 20, as well as a BSC 42 and an MSC 44. Destination network 18 may operate according to the same or a different operating protocol as originating network 14. MSCs 34, 44 each include a VLR for maintaining a register of information for all mobile phones 20 currently being served by the destination network 18. Thus, the MSCs may also be referred to as MSC/VLRs.
Transit network 16 is preferably a PSTN. Originating MSC 34 and terminating MSC 44 exchange digitized voice data over the transit network 16, in preferably an encoded Pulse Code Modulation (PCM) format, transmitted at about 64 kbps. Although PCM is a preferred encoding format, other encoding formats are available. Generally, the digitized voice data transferred over transit network 16 can be in any format which is compatible and supported by both the originating network 14 and the destination network 18.
Locating a Mobile Phone
There are many reasons why one would want to locate a mobile phone (such as a mobile phone or a pager, for example). For example, investigative agencies, such as the Federal Bureau of Investigation (FBI) and the National Security Agency (NSA) have an interest in locating persons for the purposes of law enforcement and surveillance. Likewise, private companies and individuals often need location data. For example, a Taxi company may wish to monitor the location of its cabs, or to provide them instant access to directions. Likewise, a parent may wish to know the location of a son or daughter who may be out on a date.
One service that needs location information and is highly desired by mobile phone users is the ability to use an emergency number, such as 911. Mobile phone users want to not only quickly connect to emergency services, but also have the ability to request police or other emergency assistance to their specific location (especially when the user""s location is unknown to the user). Accordingly, emergency number and location services are now in place in progressive mobile networks. Governments also have an interest in insuring that emergency services can find the caller of the emergency number.
To accelerate the rate at which mobile networks incorporate emergency numbers in their systems, in the United States the Federal Communications Commission (FCC) has recently promulgated requirements relating to emergency numbers in mobile networks. Among these requirements is that the mobile network provider be able to locate a cell phone within about ten meters of the mobile phone""s true location, when an emergency number is dialed, about 67% of the time. Other governments are implementing similar rules. To comply with these government mandates, cellular telephone service providers utilize a number of methods to locate cell phones.
Some methods of calculating the location of a mobile phone measure the time it takes for a signal to travel between a predetermined number of points in the mobile network. One method of locating a cell phone using time measurements is called the Uplink Time of Arrival (TOA) method.
The Uplink Time of Arrival method is based on measuring the time of arrival of a known signal sent from a mobile phone and received by at least three different base stations. The TOAs at different base stations are calculated and transmitted to a Mobile Positioning Center (MPC). Because of the unknown transmission time of the mobile, the MPC calculates time-difference-of-arrivals (TDOA) by pair-wise subtracting the TOA values. The mobile position can then be calculated via hyperbolic trilateration.
Handover Timing Advance (HTA) provides another method of using timing advance to locate a mobile phone. In a Time Division Multiple Access (TDMA) system the time it takes a signal to travel between the mobile phone and the serving base station must be known to avoid overlapping time slots. This time delay is called Timing Advance (TA) in the Global System for Mobile Communications (GSM). The TA can be applied to mobile positioning using a A Forced Handover method. First, at a positioning request, the network will force the MS to make a handover attempt from the serving base station to one of the neighbor cells. Then, the selected neighbor cell will measure the TA and then reject the handover request. The mobile phone will inform the serving base station about the rejection which will try another handover to another base station. This can be continued until a sufficient number of TA measurements are done by neighboring base stations. Finally, the mobile phone""s position can then be calculated from at least three TA measurements via circular trilateration.
Observed Time Difference (OTD) uses the measured timing difference of received signals to calculate the location of a mobile phone. In order create a time measurement, the mobile phone supports a xe2x80x9cpseudo-synchronous handover,xe2x80x9d whereby the mobile phone keeps track of the time it takes for signals to travel to and from neighboring base stations. The OTD then denotes the timing difference between the serving base station and neighboring base stations. With the OTDs measured to at least two neighboring base stations, the mobile phone""s position can be calculated via hyperbolic trilateration. OTD is typically executed in the mobile phone.
Another method of locating a mobile phone uses the Global Positioning System (GPS). To use GPS, a GPS receiver is located in a cell phone. The GPS receiver receives time information transmitted from satellites in orbit around the earth. The time information is received by the GPS receiver, and is then used by the GPS receiver to calculate the approximate position of the mobile phone. Then, when the cellular telephone dials an emergency number, the location of the cell phone is transmitted on the uplink channel.
Location beacons provide yet another method of identifying the location of a mobile phone. In a mobile network that uses beacons to assist in the locating of a cellular telephone, beacons are placed throughout the mobile network. For example, beacons may be placed on telephone poles, traffic lights, atop beacon towers, along buildings or other selected locations. Each beacon transmits a unique signal which identifies that beacon. Accordingly, in a beacon based location system, when an emergency number is dialed, the mobile phone transmits data containing unique beacon identification signals received by the mobile phone, as well as other information that can be used to locate the mobile phone, such as signal strengths. Afterwards, algorithms are used to calculate the location of the mobile phone.
Location Services
The service that locates the mobile phone is called a location service (LCS). Using the Taxi example from above, one commercial application provides the Taxi operator access to location information. These services may be location dependent as well. For example, the service may operate when a Taxi is in one geographic location, but not when it is in another location. Similar location dependent exclusions apply to other services as well. LCS is a new and emerging technology that is expanding rapidly in availability and scope, and as cellular networks become overloaded with LCS and other new services, the resources available to offer location services become scarce.
Besides commercial applications, LCS provide the vital service of locating a user who is at emergency. As discussed previously, the FCC places many demands on cellular systems regarding the locating of a user who is initiates an emergency service. It is therefore important that a mobile communications network be capable of coping with FCC requirementsxe2x80x94in other words, it is important to make sure that a LCS service can successfully compete for system resources versus other services, and against other non-emergency LCS requests. Unfortunately, no such methods are known. Therefore, there exist the need for methods of negotiating LCS requests for mobile communications network resources against the competing requests of other services, including other LCS services.
The present invention achieves technical advantages as a method, computer program and system that provides a location service in a mobile communications network to provide a location estimate for a terminal device associated with a user. The method takes a location request, and, with a precision that is dependent on an assigned priority level, estimates the location of a mobile phone. The computer program implements the method in software with modular programming, and the system achieves the present invention by applying a location services algorithm to a mobile communications network. Accordingly, the present invention allows flexibility in using and allocating mobile communication network resources to finding the location of mobile phones, provides additional sources of revenue for mobile communication network operators, and provides a correspondence to existing methods of handling non-location priority services, such as eMLPP.
In one embodiment, the present invention is a mobile location service that estimates the location of a mobile phone with an accuracy based on a subscriber priority. The method begins when a location request is received. Next, the user is associated with a priority level (which may be a subscribed priority level or a selected priority level) and the location request is processed to determine a location estimate for the terminal device. The precision of the location estimate is based on a priority level of the terminal device. Finally, for this embodiment, the location estimate is reported.
In another embodiment, the invention is a computer program that provides a location service in a mobile communication network, so as to provide a location estimate for a terminal device associated with a user. The computer program has a location request module for receiving a location request from a user, a location request processing module that makes a location estimate with an accuracy based on a priority level associated with the user, and a terminal device location estimation reporting module that communicates the location estimate to the user.
In yet another embodiment, the present invention is a system that provides a location service in a mobile communication network. The system has a terminal device in communication with a GMLC, a MSC coupled to the Gateway Mobile Location Center GMLC and a Serving Mobile Location Center SMLC, and is further coupled to a Base Station Controller BSC. In addition, the system has a Location Measurement Unit LMU connected to the BSC, and a location services algorithm distributed in the mobile communications network.